Temperature-dependent time-delay switch

ABSTRACT

A Miller integrator is connected to the output of a circuit the output current of which is dependent on the temperature of a temperature-dependent resistor responsive to engine temperature. A switching stage which controls the current through the starting valve of the engine is turned off when the current in the Miller integrator reaches a predetermined value after a time delay that depends on the temperature of the temperature-dependent resistor.

United States Patent Schmid Feb. 13, 1973 TEMPERATURE-DEPENDENT TIME-[56] References Cited DELAY SWITCH UNITED STATES PATENTS [75] Inventor:Hermann Schmid, Goeppingen,

Germany 3,330,970 7/1967 Wennerberg et a1. ..328/3 3,544,810 12/1970McDonald etal ..328/128 [73] Assignee: Robert Bosch, Gmbl-l, Stuttgart,3,483,851 12/1969 Reighardt. ..l23/32 EA Germany 6 PrimaryExaminer-Laurence M. oodridge [22] Ffled: Sept 1970 AttorneyMichael S.Striker [21] Appl. No.: 73,040

[57] ABSTRACT [30] F i A li ti P i it D t A Miller integrator isconnected to the output of a circuit the output current of which isdependent on the Oct. 2, l969 Germany ..P 19 49 703.1 temperature of atemperature dependent resistor responsive to engine temperature. Aswitching stage [52] 123/32 123/179 123/179 L which controls the currentthrough the starting valve hit. of h gi i turned off when the current inthe [58] held of Search-123] 179 179 180 180T Miller integrator reachesa predetermined value after 123/180 E, 179 G, 32 EA, 32 AE; 328/228,128, 3

a time delay that depends on the temperature of thetemperature-dependent resistor.

15 Claims, 2 Drawing Figures PMHHUNEU l 3 I973 INVENTOR Hermann SCHM!his ATTORN EY TEMPERATURE-DEPENDENT TIME-DELAY SWITCH BACKGROUND OF THEINVENTION The invention relates to an auxiliary starting arrangementhaving a time-delay switch, for fuel-injection internal combustionengines, the delay of the time-delay switch being dependent on thetemperature of a temperature-dependent resistor.

There are known in the prior art circuits having voltage-dependentresistors in bridge circuits. The voltage is conducted from the bridgediagonal, amplified, and then processed for-feeding a meter, forexample, or for controlling some device. Also known are electronictime-delay switches incorporating temperature-dependent resistors thatcompensate for bothersome ambient temperature fluctuations. Thecombination of known bridge circuits and known time-delay switches intoan electronic time-delay switch, and time delay of which is dependent onsome temperature, requires a very sophisticated knowledge of electroniccircuitry.

SUMMARY OF THE INVENTION An object of the invention is a simple yetefficacious time-delay arrangement that is reliable in operation andwell stabilized against ambient temperature fluctuation.

The arrangement of the invention is fully equal to the demands made onit for operation in motor vehicles.

The arrangement of the invention consists essentially of electricallyoperated starting valve means having open and closed positions, electriccircuit means, and means for simultaneously opening the valve means andenergizing the circuit means, the circuit means com prisingtemperature-dependent resistor means responsive to engine temperature, afirst circuit portion having an input and an output, the input beingconnected to the temperature-dependent resistor means so that the outputhas an output current that is dependent on the value of the resistormeans, a second circuit portion comprising a Miller integrator circuitconnected to the output, the Miller integrator circuit having also anoutput, normally conductive electronic switch means for closing thevalve means when non-conductive, the electronic switch means beingconnected to the Miller integrator circuit output to be renderednon-conductive when the current of that output reaches a predeterminedvalue.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF'TI-IE DRAWING FIG. 1 schematically shows a use ofthe invention in an internal combustion engine with fuel injection, and

FIG. 2 shows a circuit diagram of the arrangement of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1, atime-delay switch 10 is energized by the internal combustion enginestarting switch 11, shown in FIG. 1 as a vertical line with an arrow. At12 a temperature-dependent resistor (R22 in FIG. 2), responsive to thereference temperature, such as the engine temperature, provides for theswitch 10 a signal indicative of the reference temperature. Thetime-delay switch 10 opens, for an interval dependent on the referencetemperature, a starting valve 13, to which a pump 14 supplies fuel froma tank 15. As long as the starting valve 13 is open, fuel is furnishedto the intake manifold 16 of an internal combustion engine, not shown.

The arrangement operates in the following manner. If a start signal isconducted at 11 to the electronic time-delay switch 10 when the first orstarting switch 11 is closed to start up the engine, the switch 10 istriggered to its unstable state. The length of time that the switchremains in this state depends on the reference temperature, the signalof which is conducted to the switch 10 at 12. The output of thetime-delay switch 10 is connected to the electrical winding of thestarting valve 13, so that the latter is held open during thestarting-up period of the engine. During this interval of time fuel issprayed into the intake manifold 16 through the open valve 13. Once thisperiod of time is up, which period is dependent on the referencetemperature, the electronic time-delay switch 10 is triggered to itsstable state, and the starting valve 13 is again closed. After starting,for a brief period of time determined by the time-delay switch 10, anadditional amount of fuel is added to the engine. The total amount ofexcess fuel supplied depends, for example, on the temperature of theengine, so that when the latter is hot, a smaller, and when cold, alarger, amount of fuel is sprayed into the intake manifold 16.

A circuit diagram of the time-delay switch 10 is shown in FIG. 2. Thecircuit comprises temperaturesensing means 17, Miller integrator 19, andactuating means including switch 11, as well as those components to theright (in FIG. 2) of integrator 19. The actuating means has an output atthe anode of diode D30. A voltage divider, composed of thetemperature-sensitive resistor R22 and a resistor R23 connected inseries, is connected between the ground line 20 and the positive batteryline 21. The junction between the two resistors R22 and R23 is connectedto the base of a first transistor T24, the emitter of whichis connectedby a resistor R25 to an emitter-follower stage composed of a secondtransistor T26 and a resistor R27. The emitter follower transistorprovides thermal compensation, as explained below. The base oftransistor T26 is connected to the tap of a voltage divider composed ofthe series-connected resistors R28 and R29 connected between the lines20 and 21. The starting switch 11, connected to the positive supply line21, is connected to the ground or negative supply line 20 by a firstdiode D30 connected in series with a resistor R31. Consequently, theanode of the diode D30 is connected to the first or starting switch 11.A second diode D32 is connected conductively between the collector ofthe transistor T24 and the cathode of diode 30. A third diode D33 isconnected conductively between the collector of transistor T24 and thebase of a transistor T34. The Miller integrator 19 is composed oftransistors T34 and T35. The collector of transistor T34 is connected byresistor R36 to the line 21, and the emitter of this same transistor isconnected by a resistor R37 to the line 20. A resistor R38 connects thebase of transistor T35 to the base of transistor T34. The emitter oftransistor T35 is connected directly to the ground line 20, and thecollector is connected through resistor R39 to the positive line 21. Anintegrating capacitor C40 is connected between the collector oftransistor T35 and the base of transistor T34. A second switch orswitching stage, comprising the transistor T41, is connected to theMiller integrator 19. The base of transistor T41 is connected by aresistor R42 to the line 20, and by the series-connected diodes D43, D44and resistor R45 to the line 21. Components R42, D43, D44 and R45compose a voltage divider. The diodes D43 and D44 are connected toconduct. The emitter of transistor T41 is connected to the line 20, andthe collector is connected through a relay 46 to the starting switch 11,the other terminal of which is connected to the line 21. When thestarting switch 11 is closed, the relay 46 is connected in the collectorcircuit of transistor T41, and its operating contact 47 is closed whenthe transistor T41 conducts. Transistor T41 is protected against highvoltage peaks that can appear when the relay 46 opens by a diode D48shunted across the collector-emitter path of transistor T4], with thepolarity of the diode such that the diode conducts in the directionopposite to current flow along this path. The starting valve 13 isconnected in series with the relay operating contact 47. The switchingamplifier, or switching stage, is connected to the Miller integrator bya diode D49, the cathode of which is connected to the collector oftransistor T35, which latter is of an npntype. To protect transistor T41against destruction by short-circuit, its collector is connected to thebase of transistor T35 by a series-connected resistor R50 and diode D51.The electrical input to the actuating means of FIG. 2 comprises thecathode terminal of diode D49. As explained below, when the input signalfurnished by integrator 19 to the electrical input reaches apredetermined value, the aforementioned valve closes, in thisembodiment. The actuating means has an output at the anode of D30 andproduces there an integrate signal when the valve is opened.

The circuit just described operates in the following manner.

The temperature-dependent resistor R22 is always at the referencetemperature and, for example, is contained in a temperature-sensingdevice that is mounted on the internal combustion engine. At lowtempera-. tures the resistor R22 has a high resistance, and at hightemperatures a low resistance. The voltage at the base of transistor T24depends upon the temperature of re- I sistor R22. Since the emittervoltage of transistor T26 is approximately constant, because the voltagedivider R28 and R29 keeps the base of this transistor at a fixedvoltage, the current flowing through the transistor T24 depends upon thesize of the resistor R25 and upon the voltage difference between theemitters of transistors T24 and T26. When the starting switch 1 1 isclosed, the diode-resistor network 18 provides a path for the current oftransistor T24 to flow to the Miller integrator 19. If the startingswitch 1 1 is open, the first diode D30 does not conduct, and currentfrom transistor T24 flows through the second diode D32 and the resistorR31 to ground. The resistor R31 is so low in value that the Millerintegrator 19 does not conduct. If the starting switch 11 is closed,diode D30 conducts, and the cathode of diode D32 is consequentlypositive, so that this diode does not conduct. Current from thetransistor T24 flows through the de-coupling diode D33 to the base oftransistor T34 of the Miller integrator 19. At the same time that thestarting switch 11 is closed, the relay 46 is energized, since thetransistor T41 is turned on. The closing of the operating contact 47 ofthe relay 46 connects the starting valve 13 to the battery voltage,thereby opening the valve and admitting additional fuel into the intakemanifold 16. In dependence on the amount of current supplied by thetransistor T24, the Miller integrator now begins to integrate, thecollector potential of transistor T35 falling with a rapidity thatdepends on the amount of current flowing into the transistor T34 fromtransistor T24. As soon as the collector potential reaches a value atwhich the diode D49 becomes conductive, the transistor T41 turns off;the relay 46 is therefore de-energized, and the starting valve 13 isclosed.

If there is a change in the ambient temperature in which the unit 17operates, the characteristics of the two transistors T24 and T26 changein an approximately similar manner, whereby the current furnished by thetransistor T24 to the transistor T34 of the Miller integrator 19 isindependent of transistor changes associated with the ambienttemperature, but is always a function of the value of thetemperature-dependent resistor R22. The transistor T26, connected as anemitter-follower, insures in a very simple way a sufficiently accuratetemperature compensation of the first circuit portion 17. As against aswitch with movable contacts, the resistor-diode network 18 has theadvantage that no high peak voltages are conducted to the electroniccomponents, since these latter are easily harmed by excessive voltage.The use of a Miller integrator instead of a multivibrator, comprising achangeable resistor that varies the time of return to the other state,has the advantage that the Miller integrator remains continuously turnedhard on after its initial delay period; and the circuit can remainenergized without affecting the starting valve 13. The latter, forexample, cannot be accidentally operated. Only after the starting switch11 is re-opened and then re-closed does the time-delay switch 10 of theinvention begin to operate anew to actuate the starting valve 13.

The circuit of the invention also has a simple and dependableshort-circuit protection. When the engine is started up, the supplyvoltage for the electrical equip ment on the motor vehicle is providedbefore the closing of the starting switch 11. The base-emitter path oftransistor T41 is made conductive through the resistors R42 and R45, aswell as through the diodes D44 and D43. If the switch 11 is now closed,the transistor T41 is turned on very quickly, since its base-emitterpath is already at the potential necessary for conduction. The timenecessary for the path composed of the resistor R50 and the diode D51 tobecome conductive is therefore greater than the turn-on time of thetransistor T41. Once the latter is conductive, the terminal of the reinrelay 46 the collector of transistor T41 is positive,

transistor T35 is turned on and transistor T41 is therefore turned off.Only during the time that the former transistor is turning on and thelatter transistor is turning off does a short-circuit current flow.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofcircuits differing from the types described above.

While the invention has been illustrated and described as embodied in atemperature-dependent time-delay switch, it is not intended to belimited to the details shown, since various modifications and structural changes may be made without departing in any way from the spiritof the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialfeatures of the generic or specific aspects of the invention and,therefore, such adaptations should and are intended to be comprehendedwithin the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is:

1. In an auxiliary starting arrangement for a fuel-injection internalcombustion engine, in combination an electrically operatedfuel-injection valve; actuating means having an electrical input, andbeing operative for opening said valve and therewith generating anintegrate signal and for closing said valve when the input signal atsaid electrical input reaches a predetermined value; temperature-sensingmeans for producing a temperature signal indicative of a sensedtemperature associated with said engine; and integrating circuit meansfor applying to said electrical input an input signal which has aninitial value and which upon generation of said integrate signal departsfrom said initial value towards said predetermined value incorrespondence to the time integral of said temperature signal andreaches said predetermined value after a time interval the length ofwhich is a function off said temperature signal.

2. In an arrangement as defined in claim 1, said temperature sensingmeans including a temperature-dependent resistor, variations in theresistance of said resistor producing corresponding changes in the valueof said temperature signal.

3. In an arrangement as defined in claim 1, said temperature-sensingmeans including a voltage divider comprising a temperature-dependentresistor and a voltage tap, and further including a first transistorwhose base is biased by the tap voltage of said voltage divider, wherebyvariations in said sensed temperature will produce correspondingvariations in the collector current of said first transistor.

4. In an arrangement as defined in claim 2, said temperature sensingmeans further including thermal compensation means for preventingchanges in the value of said temperature signal other than thoseresulting from variations in said resistance of saidtemperature-dependent resistor, whereby said temperature signal willconstitute an accurate indication of said sensed temperature.

5. In an arrangement as defined in claim 3, said temperature sensingmeans further including thermal compensation means comprising anemitter-follower transistor in circuit with said first transistor,variations in the base-emitter voltage of said emitter-followertransistor substantially compensating corresponding variations in thebase-emitter voltage of said first transistor.

6. In an arrangement as defined in claim 1, wherein said valve has anelectrical valve control input; said actuating means including supplymeans supplying electrical energy, and further including switch means incircuit with said valve control input and supply means, for causingopening and closing of said valve.

7. In an arrangement as defined in claim 6, said switch means includingfirst and second switches connected in circuit, closing of said firstswitch causing closing of said second switch and opening of said valvefor a time interval dependent on said sensed temperature.

8. In an arrangement as defined in claim 7, said second switch being anelectronic switch provided with said electrical input, and opening whenthe signal at said electrical input reaches said predetermined value.

9. In an arrangement as defined in claim 6, said integrating circuitmeans having an input and said temperature sensing means having anoutput at which said temperature signal is produced, and said switchmeans being connected with said output of said temperature sensing meansand said input of said integrating circuit means and connecting the samewhen said valve is opened.

10. In an arrangement as defined in claim 9, said switch means includinga diode switching network connecting said output of said sensing meansand said input of said integrating circuit means.

11. In an arrangement as defined in claim 1, said integrating circuitmeans comprising a Miller integrator stage.

12. In an arrangement as defined in claim 11, said temperature sensingmeans having an output at which is generated said temperature signal,said Miller integrator stagehaving at its input a diode-resistancenetwork, said diode-resistance network connected with the output of saidtemperature sensing means and further with said actuating means.

13. In an arrangement as defined in claim 8, said electronic switchcomprising a switching transistor whose collector-emitter path isconnected in circuit with said valve control input, and said actuatingmeans further including protection means for protecting said switchingtransistor against damage due to sudden energy changes resulting uponopening and closing of said electrically operated valve.

14. In an arrangement as defined in claim 13, said. protection meansincluding current shunt means connected in circuit with said switchingtransistor for furnish to said electrical input of said switchingtransistor an input signal causing said switching transistor to becomenon-conductive when the collector-emitter voltage thereacrosssubstantially reaches a predetermined undesired value.

1. In an auxiliary starting arrangement for a fuel-injection internalcombustion engine, in combination an electrically operatedfuel-injection valve; actuating means having an electrical input, andbeing operative for opening said valve and therewith generating anintegrate signal and for closing said valve when the input signal atsaid electrical input reaches a predetermined value; temperature-sensingmeans for producing a temperature signal indicative of a sensedtemperature associated with said engine; and integrating circuit meansfor applying to said electrical input an input signal which has aninitial value and which upon generation of said integrate signal departsfrom said initial value towards said predetermined value incorrespondence to the time integral of said temperature signal andreaches said predetermined value after a time interval the length ofwhich is a function off said temperature signal.
 1. In an auxiliarystarting arrangement for a fuel-injection internal combustion engine, incombination an electrically operated fuel-injection valve; actuatingmeans having an electrical input, and being operative for opening saidvalve and therewith generating an integrate signal and for closing saidvalve when the input signal at said electrical input reaches apredetermined value; temperature-sensing means for producing atemperature signal indicative of a sensed temperature associated withsaid engine; and integrating circuit means for applying to saidelectrical input an input signal which has an initial value and whichupon generation of said integrate signal departs from said initial valuetowards said predetermined value in correspondence to the time integralof said temperature signal and reaches said predetermined value after atime interval the length of which is a function off said temperaturesignal.
 2. In an arrangement as defined in claim 1, said temperaturesensing means including a temperature-dependent resistor, variations inthe resistance of said resistor producing corresponding changes in thevalue of said temperature signal.
 3. In an arrangement as defined inclaim 1, said temperature-sensing means including a voltage dividercomprising a temperature-dependent resistor and a voltage tap, andfurther including a first transistor whose base is biased by the tapvoltage of said voltage divider, whereby variations in said sensedtemperature will produce corresponding variations in the collectorcurrent of said first transistor.
 4. In an arrangement as defined inclaim 2, said temperature sensing means further including thermalcompensation means for preventing changes in the value of saidtemperature signal other than those resulting from variations in saidresistance of said temperature-dependent resistor, whereby saidtemperature signal will constitute an accurate indication of said sensedtemperature.
 5. In an arrangement as defined in claim 3, saidtemperature sensing means further including thermal compensation meanscomprising an emitter-follower transistor in circuit with said firsttransistor, variations in the base-emitter voltage of saidemitter-follower transistor substantially compensating correspondingvariations in the base-emitter voltage of said first transistor.
 6. Inan arrangement as defined in claim 1, wherein said valve has anelectrical valve control input; said actuating means including supplymeans supplying electrical energy, and further including switch means incircuit with said valve control input and supply means, for causingopening and closing of said valve.
 7. In an arrangement as defined inclaim 6, said switch means including first and second switches connectedin circuit, closing of said first switch causing closing of said secondswitch and opening of said valve for a time interval dependent on saidsensed temperature.
 8. In an arrangement as defined in claim 7, saidsecond switch being an electronic switch provided with said electricalinput, and opening when the signal at said electrical input reaches saidpredetermined value.
 9. In an arrangement as defined in claim 6, saidintegrating circuit means having an input and said temperature sensingmeans having an output at which said temperature signal is produced, andsaid switch means being connected with said output of said temperaturesensing means and said input of said integrating circuit means andconnecting the same when said valve is opened.
 10. In an arrangement asdefined in claim 9, said switch means including a diode switchingnetwork connecting said output of said sensing means and said input ofsaid integrating circuit means.
 11. In an arrangement as defined inclaim 1, said integrating circuit means comprising a Miller integratorstage.
 12. In an arrangement as defined in claim 11, said temperaturesensing means having an output at which is generated said temperaturesignal, said Miller integrator stage having at its input adiode-resistance network, said diode-resistance network connected withthe output of said temperature sensing means and further with saidactuating means.
 13. In an arrangement as defined in claim 8, saidelectronic switch comprising a switching transistor whosecollector-emitter path is connected in circuit with said valve controlinput, and said actuating means further including protection means forprotecting said switching transistor against damage due to sudden energychanges resulting upon opening and closing of said electrically operatedvalve.
 14. In an arrangement as defined in claim 13, said protectionmeans including current shunt means connected in circuit with saidswitching transistor for shunting excessive currents away from saidswitching transistor.